The present invention relates to granular bleach activators having improved solubility profiles for use in detergent and textile treatment applications.
Recently, there has been considerable interest within the detergent industry concerning laundry detergents that have the convenience, aesthetics and solubility of liquid laundry detergent products, but that retain the cleaning performance and cost of granular detergent products especially those with bleach activators. The problems, however, associated with past granular compositions with regard to aesthetics, solubility and user convenience are formidable. Such problems have been exacerbated by the advent of xe2x80x9ccompactxe2x80x9d or low dosage granular products that typically do not dissolve rapidly in washing solutions. These low dosage granular products are currently in high demand as they conserve resources and can be sold in small packages which are more convenient for consumers prior to use, but which are less convenient when dispensed into the washing machine as compared to liquid laundry products that are simply poured directly from the bottle.
Low dosage or xe2x80x9ccompactxe2x80x9d laundry products containing bleach activators unfortunately experience dissolution problems, especially in cold temperature laundering solutions (i.e., less than about 30xc2x0 C.). More specifically, poor dissolution results in the formation of xe2x80x9cclumpsxe2x80x9d which appear as solid white masses remaining in the washing machine or on the laundered clothes after conventional washing cycles. These xe2x80x9cclumpsxe2x80x9d are especially prevalent under cold temperature washing conditions and/or when the order of addition to the washing machine is laundry detergent first, clothes second and water last (commonly known as the xe2x80x9cReverse Order Of Additionxe2x80x9d or xe2x80x9cROOAxe2x80x9d). Such undesirable xe2x80x9cclumpsxe2x80x9d also form if the consumer loads the washing machine in the order of: clothes, detergent and then water.
This clumping phenomenon can contribute to the incomplete dispensing of granular laundry products in washing machines equipped with dispenser drawers or in other dispensing devices, such as a granulette. In this case, the undesired result is undissolved detergent and bleach activator residue in the dispensing device.
Granular bleach activators are commonly used in combination with detersive surfactants and detergent builders in various detergent compositions. In such compositions, it has been found that the cause of the aforementioned dissolution problem is associated with the xe2x80x9cbridgingxe2x80x9d of a xe2x80x9cgel-likexe2x80x9d substance between surfactant-containing particles to form undesirable xe2x80x9cclumps.xe2x80x9d The gel-like substance responsible for the undesirable bridging of particles into clumps originates from the partial dissolution of surfactant in the aqueous laundering solutions, wherein such partial dissolution causes the formation of a highly viscous surfactant phase or paste which binds or otherwise bridges other surfactant-containing particles together into clumps. This undesirable dissolution phenomena is commonly referred to as xe2x80x9clump-gelxe2x80x9d formation.
In addition to the viscous surfactant bridging effect, inorganic salts have a tendency to hydrate which can also cause bridging of particles which are linked together via hydration. In particular, inorganic salts hydrate with one another to form a cage structure which exhibits poor dissolution and ultimately ends up as a clump after the washing cycle. It would therefore be desirable to have a detergent composition that does not experience the dissolution problems identified above so as to result in improved cleaning performance.
The prior art is replete with disclosures addressing the dissolution problems associated with granular detergent compositions containing bleach activator particles. For example, the prior art suggests limiting the use and manner of inorganic salts that can cause clumps via the bridging of hydrated salts during the laundering cycle. Specific ratios of selected inorganic salts are contemplated so as to minimize dissolution problems. Such a solution, however, constricts the formulation and process flexibility that is necessary for current commercialization of large-scale detergent products. Various other mechanisms have been suggested by the prior art, all of which involve formulation alteration, and thereby reduce formulation flexibility. As a consequence, it would therefore be desirable to have a detergent composition having improved dissolution without significantly inhibiting formulation flexibility. Accordingly, there remains a need to identify a mechanistic approach to the performance of granular detergent compositions and their granular components over a broad range of conditions and for a granular composition that has improved dispersion and solubility over conventional granular detergent and compositions. The identification and controlled production of granular bleach activators that will contribute to such improvements in dispersion and solubility without constricting formulation flexibility are essential.
A further problem associated with granular detergents is the separation of detergent components during transport and storage prior to use. This separation is largely due to the presence of different detergent components that have different sizes, shapes and weight. Over time and through movements or vibration of the composition, smaller, heavier components tends to settle towards the bottom of the detergent container. This separation of the detergent composition components can result in the consumer dispensing a composition which no longer contains the intended detergent formulation. The prior art has attempted to overcome this problem by combining all of the detergent components in a single particle or agglomerate that cannot separate, but many of these components are reactive and tend to degrade when combined in this manner. Thus, there remains a need for a detergent composition wherein the granular components are of a relatively uniform size and shape to thereby inhibit this separation effect.
Still yet another problem associated with the formation of bleach activator granules is in production of extruded granules or particulates that have a relatively uniform size, and shape. Typically, bleach activators are extruded and then ground to an approximate size. However, grinding is a inexact process and it tends to produce copious amounts of fines and overs that must be separated from the target sized granules and recycled or otherwise handled. Thus, there also remains a need for a process that will enable the production of bleach activators having uniform size and shape that are selected by the formulator.
Granular bleach activators may also be used in various processes in the production of textiles. Although the dissolution problems that are believed to be associated with the presence of detersive surfactants and inorganic salts may not be present in such applications, the availability of a granular bleach activator extrudate having uniform physical and performance characteristics, including good solubility, is also highly desired.
In accordance with one aspect of the invention, a cylindrically-shaped bleach activator extrudate having uniform length and diameter are provided. The bleach activators have the general formula: 
wherein R is an alkyl group containing from about 5 to about 18 carbon atoms wherein the longest linear alkyl chain extending from and including the carbonyl carbon contains from about 6 to about 12 carbon atoms and L is a leaving group, the conjugate acid of which has a pKxcex1 in the range of from about 6 to about 13, and wherein said bleach activator is in the form of a cylindrically-shaped particle having a mean particle diameter of from about 450 microns to about 1000 microns and a mean extrudate length of from about 450 microns to about 3500 microns. The cylindrically-shaped bleach activator extrudate has improved solubility, flowability and reduced product settlement or separation when mixed with other granular materials, such as in a granular detergent composition.
In a further aspect of the present invention, a granular detergent composition containing a cylindrically-shaped bleach activator having a uniform diameter and length is provided. The granular detergent composition contains a particulate detersive surfactant, particulate detergent builder and an effective amount of cylindrically-shaped bleach activator granules, wherein the bleach activator granules have substantially the same diameter and length as the particulate surfactant and builder. The granular detergent composition exhibits improved solubility, flowability and reduced product settlement during storage. Accordingly, it is an object of the invention to provide a detergent composition containing bleach activator particles that have good stability prior to use and acceptable physical properties.
In accordance with a process aspect of the invention, a method of extruding bleach activators so as to produce granules having uniform diameter and length is provided. The method comprises the steps of passing the bleach activator material through a heated die having a desired diameter and shape, cutting the extrudate at a desired frequency, and rapidly cooling the cut extrudate.
These and other objects, features and attendant advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description of the preferred embodiment and the appended claims.